1. Field of the Invention
The present invention relates to novel compounds having retinoid-like biological activity. More specifically, the present invention relates to amines substituted with a dihydronaphthalenyl, chromenyl, or thiochromenyl group, an aryl or heteroaryl group and an alkyl group, which have retinoid-like, retinoid antagonist or retinoid inverse agonist-like biological activity.
2. Background Art
Compounds which have retinoid-like activity are well known in the art, and are described in numerous United States and other patents and in scientific publications. It is generally known and accepted in the art that retinoid-like activity is useful for treating animals of the mammalian species, including humans, for curing or alleviating the symptoms and conditions of numerous diseases and conditions. In other words, it is generally accepted in the art that pharmaceutical compositions having a retinoid-like compound or compounds as the active ingredient are useful as regulators of cell proliferation and differentiation, and particularly as agents for treating skin-related diseases, including, actinic keratoses, arsenic keratoses, inflammatory and non-inflammatory acne, psoriasis, ichthyoses and other keratinization and hyperproliferative disorders of the skin, eczema, atopic dermatitis, Darriers disease, lichen planus, prevention and reversal of glucocorticoid damage (steroid atrophy), as a topical anti-microbial, as skin anti-pigmentation agents and to treat and reverse the effects of age and photo damage to the skin. Retinoid compounds are also useful for the prevention and treatment of cancerous and precancerous conditions, including, premalignant and malignant hyperproliferative diseases such as cancers of the breast, skin, prostate, cervix, uterus, colon, bladder, esophagus, stomach, lung, larynx, oral cavity, blood and lymphatic system, metaplasias, dysplasias, neoplasias, leukoplakias and papillomas of the mucous membranes and in the treatment of Kaposi""s sarcoma. In addition, retinoid compounds can be used as agents to treat diseases of the eye, including, without limitation, proliferative vitreoretinopathy (PVR), retinal detachment, dry eye and other comeopathies, as well as in the treatment and prevention of various cardiovascular diseases, including, without limitation, diseases associated with lipid metabolism such as dyslipidemias, prevention of post-angioplasty restenosis and as an agent to increase the level of circulating tissue plasminogen activator (TPA). Other uses for retinoid compounds include the prevention and treatment of conditions and diseases associated with human papilloma virus (HPV), including warts and genital warts, various inflammatory diseases such as pulmonary fibrosis, ileitis, colitis and Krohn""s disease, neurodegenerative diseases such as Alzheimer""s disease, Parkinson""s disease and stroke, improper pituitary function, including insufficient production of growth hormone, modulation of apoptosis, including both the induction of apoptosis and inhibition of T-Cell activated apoptosis, restoration of hair growth, including combination therapies with the present compounds and other agents such as MinoxidilR, diseases associated with the immune system, including use of the present compounds as immunosuppressants and immunostimulants, modulation of organ transplant rejection and facilitation of wound healing, including modulation of chelosis. Retinoid compounds have relatively recently been also discovered to be useful for treating type II non-insulin dependent diabetes mellitus (NIDDM).
Although pharmaceutical compositions containing retinoids have well established utility, retinoids also cause a number of undesired side effects at therapeutic dose levels, including headache, teratogenesis, mucocutaneous toxicity, musculoskeletal toxicity, dyslipidemias, skin irritation, headache and hepatotoxicity. These side effects limit the acceptability and utility of retinoids for treating disease.
It is now general knowledge in the art that two main types of retinoid receptors exist in mammals (and other organisms). The two main types or families of receptors are respectively designated the RARs and RXRs. Within each type there are subtypes; in the RAR family the subtypes are designated RARxcex1, RARxcex2 and RARxcex3, in RXR the subtypes are: RXRxcex1, RXRxcex2 and RXPxcex3. It has also been established in the art that the distribution of the two main retinoid receptor types, and of the several sub-types is not uniform in the various tissues and organs of mammalian organisms. Moreover, it is generally accepted in the art that many unwanted side effects of retinoids are mediated by one or more of the RAR receptor subtypes. Accordingly, among compounds having agonist-like activity at retinoid receptors, specificity or selectivity for one of the main types or families, and even specificity or selectivity for one or more subtypes within a family of receptors, is considered a desirable pharmacological property. Some compounds bind to one or more RAR receptor subtypes, but do not trigger the response which is triggered by agonists of the same receptors. A compound that binds to a biological receptor but does not trigger an agonist-like response is usually termed an antagonist. Accordingly, the xe2x80x9ceffectxe2x80x9d of compounds on retinoid receptors may fall in the range of having no effect at all, (inactive compound, neither agonist nor antagonist) or the compound may elicit an agonist-like response on all receptor subtypes (pan-agonist). As still another alternative a compound may be a partial agonist and/or partial antagonist of certain receptor subtypes if the compound binds to but does not activate certain receptor subtype or subtypes but elicits an agonist-like response in other receptor subtype or subtypes. A pan-antagonist is a compound that binds to all known retinoid receptors but does not elicit an agonist-like response in any of the receptors.
Recently a two-state model for certain receptors, including the above-mentioned retinoid receptors, have emerged. In this model, an equilibrium is postulated to exist between inactive receptors and spontaneously active receptors which are capable of coupling with a G protein in the absence of a ligand (agonist). In this model, so-called xe2x80x9cinverse agonistsxe2x80x9d shift the equilibrium toward inactive receptors, thus bringing about an overall inhibitory effect. Neutral antagonists do not effect the receptor equilibrium but are capable of competing for the receptors with both agonists (ligands) and with inverse agonists. U.S. Pat. No. 5,877,207 titled xe2x80x9cSynthesis and Use of Retinoid Compounds Having Negative Hormone and/or Antagonist Activitiesxe2x80x9d describes the foregoing two-state model and the use of retinoid antagonist and negative hormones in detail.
Among the scientific publications Dawson and William H. Okamura, Chemistry and Biology of Synthetic Retinoids, published by CRC Press Inc., 1990, pages 334-335, 354 and 324-356 is of special interest as an overview of the prior art on the subject.
Among United States and foreign patents which disclose compounds having retinoid agonist, antagonist or inverse agonist like biological activity and are known to applicant the following examples include diaryl or heteroaryl substituted amines and are therefore of interest as background to the present invention: WO9845242-A1, published on Oct. 15, 1998, and French patent application number 94 05019, laid-over-to-public-inspection on Oct. 27, 1995. Published Japanese Application JP63132864 (Chemical Abstracts 110: 25516, (1988)) and U.S. Pat. No. 4,898,872 (Chemical Abstracts 110: 231627) disclose amines substituted with a tetrahydroquinolin-6-yl and/or tetrahydroquinolinone-6-yl group and an aryl and optionally with an alkyl group, however these compounds are not described as retinoids.
Among the numerous United States and foreign patents which disclose compounds having retinoid agonist, antagonist or inverse agonist like biological activity and are known to applicant, the following examples include a dihydronaphthalene, chromen, thiochromen or dihydroquinoline ring structure and are therefore of interest as background to the present invention: U.S. Pat. Nos. 5,773,594; 5,808,083; 5,808,124; 5,877,207; 5,952,345; 5,958,954; 5,618,931; 5,489,584; 5,559,248; 5,648,514 and EPO 0 661 259 A1.
The present invention relates to compounds of Formula 1
where X is O, S, or C(R)2;
R is H or alkyl of 1 to 6 carbons;
R1 is H, alkyl of 1 to 10 carbons, alkenyl of 2 to 6 carbons, phenyl-C1-C6 alkyl, or C1-C6-alkylphenyl;
R2 is H, alkyl of 1 to 6 carbons, F, Cl, Br, I, CF3, fluoro substituted alkyl of 1 to 6 carbons, alkoxy of 1 to 6 carbons, or alkylthio of 1 to 6 carbons;
R3 is independently alkyl of 1 to 6 carbons, F, Cl, Br, I, CF3, fluoro substituted alkyl of 1 to 6 carbons, OH, SH, alkoxy of 1 to 6 carbons, fluoroalkoxy of 1 to 6 carbons, alkylthio of 1 to 6 carbons; benxyloxy, C1-C6 alkyl substituted benzyloxy, halogen substituted benzyloxy, phenyloxy, C1-C6 alkyl substituted phenyloxy, or halogen substituted phenyloxy;
R4 is independently H, alkyl of 1 to 6 carbons, or F; Y is a phenyl or naphthyl group, or heteroaryl selected from a group consisting of pyridyl, thienyl, furyl, pyridazinyl, pyrimidinyl, pyrazinyl, thiazolyl, oxazolyl, imidazolyl and pyrrazolyl, said phenyl and heteroaryl groups being optionally substituted with one or two R2 groups;
m is an integer having the values 0 to 3;
o is an integer having the values 0 to 4;
A is (CH2)q where q is 0-5, lower branched chain alkyl having 3-6 carbons, cycloalkyl having 3-6 carbons, alkenyl having 2-6 carbons and 1 or 2 double bonds, alkynyl having 2-6 carbons and 1 or 2 triple bonds, and
B is hydrogen, COOH, COOR8, CONR9R10, xe2x80x94CH2OH, CH2OR11, CH2OCOR11, CHO, CH(OR12)2, CHOR13O, xe2x80x94COR7, CR7(OR12)2, CR7OR13O, or tri-lower alkylsilyl, where R7 is an alkyl, cycloalkyl or alkenyl group containing 1 to 5 carbons, R8 is an alkyl group of 1 to 10 carbons or trimethylsilylalkyl where the alkyl group has 1 to 10 carbons, or a cycloalkyl group of 5 to 10 carbons,. or R8 is phenyl or lower alkylphenyl, R9 and R10 independently are hydrogen, an alkyl group of 1 to 10 carbons, or a cycloalkyl group of 5-10 carbons, or phenyl or lower alkylphenyl, R11 is lower alkyl, phenyl or lower alkylphenyl, R12 is lower alkyl, and R13 is divalent alkyl radical of 2-5 carbons, or a pharmaceutically acceptable salt of said compound.
In a second aspect, this invention relates to the use of the compounds of Formula 1 for the treatment of skin-related diseases, including, without limitation, actinic keratoses, arsenic keratoses, inflammatory and non-inflammatory acne, psoriasis, ichthyoses and other keratinization and hyperproliferative disorders of the skin, eczema, atopic dermatitis, Darriers disease, lichen planus, prevention and reversal of glucocorticoid damage (steroid atrophy), as a topical anti-microbial, as skin anti-pigmentation agents and to treat and reverse the effects of age and photo damage to the skin. The compounds are also useful for the prevention and treatment of metabolic diseases such as type II non-insulin dependent diabetes mellitus (NIDDM) and for prevention and treatment of cancerous and precancerous conditions, including, premalignant and malignant hyperproliferative diseases such as cancers of the breast, skin, prostate, cervix, uterus, colon, bladder, esophagus, stomach, lung, larynx, oral cavity, blood and lymphatic system, metaplasias, dysplasias, neoplasias, leukoplakias and papillomas of the mucous membranes and in the treatment of Kaposi""s sarcoma. In addition, the present compounds can be used as agents to treat diseases of the eye, including, without limitation, proliferative vitreoretinopathy (PVR), retinal detachment, dry eye and other corneapathies, as well as in the treatment and prevention of various cardiovascular diseases, including, without limitation, diseases associated with lipid metabolism such as dyslipidemias, prevention of post-angioplasty restenosis and as an agent to increase the level of circulating tissue plasminogen activator (TPA). Other uses for the compounds of the present invention include the prevention and treatment of conditions and diseases associated with Human papilloma virus (HPV), including warts and genital warts, various inflammatory diseases such as pulmonary fibrosis, ileitis, colitis and Krohn""s disease, neurodegenerative diseases such as Alzheimer""s disease, Parkinson""s disease and stroke, improper pituitary function, including insufficient production of growth hormone, modulation of apoptosis, including both the induction of apoptosis and inhibition of T-Cell activated apoptosis, restoration of hair growth, including combination therapies with the present compounds and other agents such as MinoxidilR, diseases associated with the immune system, including use of the present compounds as immunosuppressants and immunostimulants, modulation of organ transplant rejection and facilitation of wound healing, including modulation of chelosis.
Alternatively, those compounds of the invention which act as antagonists or inverse agonists of one or more retinoid receptor subtypes are useful to prevent certain undesired side effects of retinoids which are administered for the treatment or prevention of certain diseases or conditions. For this purpose the retinoid antagonist and/or inverse agonist compounds of the invention may be co-administered with retinoids. The retinoid antagonist and inverse agonist compounds of the present invention are also useful in the treatment of acute or chronic toxicity resulting from overdose or poisoning by retinoid drugs or Vitamin A.
Generally speaking, the second aspect of the invention relates to the use of the novel compounds to prevent or treat diseases and conditions which are responsive to compounds that promote the expression of or bind to receptors belonging to the steroid or thyroid receptor superfamily.
This invention also relates to pharmaceutical formulations comprising a compound of Formula 1 in admixture with a pharmaceutically acceptable excipient, said formulation being adapted for administration to a mammal, including a human being, to treat or alleviate the conditions which were described above as treatable by retinoids, to be co-administered with retinoids to eliminate or reduce side effects of retinoids, or to treat retinoid or Vitamin A overdose or poisoning.
A classic measure of retinoic acid activity involves measuring the effects of retinoic acid on ornithine decarboxylase. The original work on the correlation between retinoic acid and a decrease in cell proliferation was done by Verma and Boutwell, Cancer Research, 1977, 37, 2196-2201. That reference discloses that ornithine decarboxylase (ODC) activity increased precedent to polyamine biosynthesis. It has been established elsewhere that increases in polyamine synthesis can be correlated or associated with cellular proliferation. Thus, if ODC activity could be inhibited, cell hyperproliferation could be modulated. Although all cases for ODC activity increases are unknown, it is known that 12-0-tetradecanoylphorbol-13-acetate (TPA) induces ODC activity. Retinoic acid inhibits this induction of ODC activity by TPA. An assay essentially following the procedure set out in Cancer Research: 1662-1670,1975 may be used to demonstrate inhibition of TPA induction of ODC by compounds of this invention. xe2x80x9cIC60xe2x80x9d is that concentration of the test compound which causes 60% inhibition in the ODC assay. By analogy, xe2x80x9cIC80xe2x80x9d, for example, is that concentration of the test compound which causes 80% inhibition in the ODC assay.
Other assays described below, measure the ability of the compounds of the present invention to bind to, and/or activate various retinoid receptor subtypes. When in these assays a compound binds to a given receptor subtype and activates the transcription of a reporter gene through that subtype, then the compound is considered an agonist of that receptor subtype. Conversely, a compound is considered an antagonist of a given receptor subtype if in the below described co-tranfection assays the compound does not cause significant transcriptional activation of the receptor regulated reporter gene, but nevertheless binds to the receptor with a Kd value of less than approximately 1 micromolar. In the below described assays the ability of the compounds to bind to RARxcex1, RARxcex2, RARxcex3, RXRxcex1, RXRxcex2 and RXRxcex3 receptors, and the ability or inability of the compounds to activate transcription of a reporter gene through these receptor subtypes can be tested. These assays are expected to demonstrate that the compounds of the present invention act as agonists of one or more of the above-described receptors. However, some of the compounds of the invention may behave as retinoid antagonists or partial antagonists and/or as inverse agonists. Because of the complex distribution of the different retinoid receptors in various organs of the mammalian body partial agonists and partial antagonists and compounds which have the characteristics of both may lend themselves to particularly useful therapeutic applications and may avoid serious side effects of conventional retinoid drugs.
As far as specific assays are concerned to demonstrate the activities of the compounds of the present invention, a chimeric receptor transactivation assay which tests for agonist-like activity in the RARxcex1, RARxcex2, RARxcex3, RXRxcex1 receptor subtypes, and which is based on work published by Feigner P. L. and Holm M. (1989) Focus, 112 is described in detail in U.S. Pat. No. 5,455,265. The specification of U.S. Pat. No. 5,455,265 is hereby expressly incorporated by reference.
A holoreceptor transactivation assay and a ligand binding assay which measure the antagonist/agonist like activity of the compounds of the invention, or their ability to bind to the several retinoid receptor subtypes, respectively, are described in published PCT Application No. WO WO93/11755 (particularly on pages 30-33 and 37-41) published on Jun. 24, 1993, the specification of which is also incorporated herein by reference. A detailed experimental procedure for holoreceptor transactivations has been described by Heyman et al. Cell 68, 397-406, (1992); Allegretto et al. J. Biol. Chem. 268, 26625-26633, and Mangelsdorf et al. The Retinoids: Biology, Chemistry and Medicine, pp 319-349, Raven Press Ltd., New York, which are expressly incorporated herein by reference. The results obtained in this assay are expressed in EC50 numbers, as they are also in the chimeric receptor transactivation assay. The results of ligand binding assay are expressed in Kd numbers. (See Cheng et al. Biochemical Pharmacology Vol. 22 pp 3099-3108, expressly incorporated herein by reference.)
Still another transactivation assay, the xe2x80x9cPGR assayxe2x80x9d is described in the publication Klein et al. J. Biol. Chem. 271, 22692-22696 (1996) which is expressly incorporated herein by reference, and a detailed description is also provided below. The results of the PGR assay are also expressed in EC50 numbers (nanomolar concentration).
CV-1 cells (4xc3x97105 cells/well) were transiently transfected with the luciferase reporter plasmid MTV-4(R5G)-Luc (0.7 ug/well) containing four copies of the R5G retinoid DNA response element along with the RXRxcex1 expression plasmid pRS-hRXRxcex1 (0.1 ug/well) and one of the RAR-P-GR expression plasmids (0.05 ug/well) in 12 well plates via calcium phosphate precipitation Chen et al. (1987) Mol. Cell. Biol. 7, 2745-2752 as described by Klein et al. in J. Biol. Chem. 271, 22692, referenced above. The three different RAR-P-GR expression plasmids, pRS-RARxcex1-P-GR, pcDNA3-RARxcex2-P-GR and pcDNA3-RARxcex3-P-GR, express RARxcex1, RARxcex2 and RARxcex3 receptors, respectively, which contain modified DNA binding domains such that their xe2x80x9cP-boxesxe2x80x9d have been altered to that of the glucocorticoid receptor. These RAR-P-GR receptors bind to DNA as heterodimeric complexes with RXR. Specifically, the RAR-P-GR receptors bind retinoic acid response elements designated R5G, comprised of two RAR half sites (nucleotide sequence 5xe2x80x2-GGTTCA-3xe2x80x2) separated by 5 base pairs in which the 3xe2x80x2-half site has been modified to that of a glucocorticoid receptor half site, 5xe2x80x2-AGAACA-3xe2x80x2. To allow for various in transfection efficiency a xcex2-galactosidase expression plasmid (0.01 ug/well) was used as an internal control. Alternatively, the assay was performed in a 96-well microtiter plate format (5000 cells/well) in a manner which was identical to that described above except ⅕ of the amount of the DNA-calcium phosphate precipitant (20 xcexcl instead of 100 xcexcl) was applied to each well. Eighteen hours after introduction of the DNA precipitants, cells were rinsed with phosphate buffered saline (PBS) and fed with D-MEM (Gibco-BRL) containing 10% activated charcoal extracted fetal bovine serum (Gemini Bio-Products). Cells were treated for 18 hours with the compounds indicated in the figures. After rinsing with PBS cells were lysed with luciferase activity was measured as previously described in de Wet (1987) Mol. Cell. Biol. 7, 725-737. Luciferase values represent the meanxc2x1SEM of triplicate determinations normalized to xcex2-galactosidase activity.
Inverse agonists are ligands that are capable of inhibiting the basal receptor activity of unliganded receptors. Recently, retinoic acid receptors (RARs) have been shown to be responsive to retinoid inverse agonists in regulating basal gene transcriptional activity. Moreover, the biological effects associated with retinoid inverse agonists are distinct from those of retinoid agonists or antagonists. For example, RAR inverse agonists, but not RAR neutral antagonists, cause a dose-dependent inhibition of the protein MRP-8 in cultured human keratinocytes differentiated with serum. MRP-8 is a specific marker of cell differentiation, which is also highly expressed in psoriatic epidermis, but is not detectable in normal human skin. Thus, retinoid inverse agonists may offer a unique way of treating diseases such as psoriasis.
The activity of retinoid inverse agonists can be tested by the procedure of Klein et al J. Biol. Chem. 271, 22692-22696 (1996) which is expressly incorporated herein by reference. In this assay, retinoid inverse agonists are able to repress the basal activity of a RARxcex3-VP-16 chimeric receptor where the constituitively active domain of the herpes simplex virus (HSV) VP-16 is fused to the N-terminus of RARxcex3. CV-1 cells are cotransfected with RARxcex3-VP-16, an ER-RXRxcex1 chimeric receptor and an ERE-tk-Luc chimeric reporter gene to produce a basal level of luciferase activity, as shown by Nagpal et al. EMBO J. 12, 2349 -2360 (1993) expressly incorporated herein by reference. Retinoid inverse agonists are able to inhibit the basal luciferase activity in these cells in a dose dependent manner and IC50measured. A detailed description of the tests used for determining whether or not a compound is a retinoid antagonist or inverse agonist, and the manner of utilizing retinoid antagonists and inverse agonists is provided in U.S. Pat. No. 5,877,207, the specification of which is expressly incorporated herein by reference.
Table 1 discloses the activity of certain exemplary compounds of the invention in the above-described chimeric receptor transactivation assay, holoreceptor transactivation assay and a ligand binding assays. Particularly, the transactivation data pertaining to RAR receptors were obtained in the chimeric assay, and the data pertaining to transactivation of RXR receptors were obtained in the holoreceptor transactivation assay.
As it can be seen from the foregoing assay results the preferred compounds of the invention are specific or selective agonists of RXR receptors.
The compounds of this invention may be administered systemically or topically, depending on such considerations as the condition to be treated, need for site-specific treatment, quantity of drug to be administered, and numerous other considerations.
Thus, in the treatment of dermatoses, it will generally be preferred to administer the drug topically, though in certain cases such as treatment of severe cystic acne or psoriasis, oral administration may also be used. Any common topical formulation such as a solution, suspension, gel, ointment, or salve and the like may be used. Preparation of such topical formulations are well described in the art of pharmaceutical formulations as exemplified, for example, by Remington""s Pharmaceutical Science, Edition 17, Mack Publishing Company, Easton, Pa. For topical application, these compounds could also be administered as a powder or spray, particularly in aerosol form. If the drug is to be administered systemically, it may be confected as a powder, pill, tablet or the like or as a syrup or elixir suitable for oral administration. For intravenous or intraperitoneal administration, the compound will be prepared as a solution or suspension capable of being administered by injection. In certain cases, it may be useful to formulate these compounds by injection. In certain cases, it may be useful to formulate these compounds in suppository form or as extended release formulation for deposit under the skin or intramuscular injection.
Other medicaments can be added to such topical formulation for such secondary purposes as treating skin dryness; providing protection against light; other medications for treating dermatoses; medicaments for preventing infection, reducing irritation, inflammation and the like.
Treatment of dermatoses or any other indications known or discovered to be susceptible to treatment by retinoic acid-like compounds will be effected by administration of the therapeutically effective dose of one or more compounds of the instant invention. A therapeutic concentration will be that concentration which effects reduction of the particular condition, or retards its expansion. In certain instances, the compound potentially may be used in prophylactic manner to prevent onset of a particular condition.
A useful therapeutic or prophylactic concentration will vary from condition to condition and in certain instances may vary with the severity of the condition being treated and the patient""s susceptibility to treatment. Accordingly, no single concentration will be uniformnly useful, but will require modification depending on the particularities of the disease being treated. Such concentrations can be arrived at through routine experimentation. However, it is anticipated that in the treatment of, for example, acne, or similar dermatoses, that a formulation containing between 0.01 and 1.0 milligrams per milliliter of formulation will constitute a therapeutically effective concentration for total application. If administered systemically, an amount between 0.01 and 5 mg per kg of body weight per day would be expected to effect a therapeutic result in the treatment of many diseases for which these compounds are useful.
The partial or pan retinoid antagonist and/or retinoid inverse agonist compounds of the invention, when used to take advantage of their antagonist and/or inverse agonist property, can be co-administered to mammals, including humans, with retinoid agonists and, by means of pharmacological selectivity or site-specific delivery, preferentially prevent the undesired effects of certain retinoid agonists. The antagonist and/or inverse agonist compounds of the invention can also be used to treat Vitamin A overdose, acute or chronic, resulting either from the excessive intake of vitamin A supplements or from the ingestion of liver of certain fish and animals that contain high levels of Vitamin A. Still further, the antagonist and/or inverse agonist compounds of the invention can also be used to treat acute or chronic toxicity caused by retinoid drugs. It has been known in the art that the toxicities observed with hypervitaminosis A syndrome (headache, skin peeling, bone toxicity, dyslipidemias) are similar or identical with toxicities observed with other retinoids, suggesting a common biological cause, that is RAR activation. Because the antagonist or inverse agonist compounds of the present invention block or diminish RAR activation, they are suitable for treating the foregoing toxicities.
Generally speaking, for therapeutic applications in mammals, the antagonist and/or inverse agonist compounds of the invention can be administered enterally or topically as an antidote to vitamin A, or antidote to retinoid toxicity resulting from overdose or prolonged exposure, after intake of the causative factor (vitamin A, vitamin A precursor, or other retinoid) has been discontinued. Alternatively, the antagonist and/or inverse agonist compounds of the invention are co-administered with retinoid drugs, in situations where the retinoid provides a therapeutic benefit, and where the co-administered antagonist and/or inverse agonist compound alleviates or eliminates one or more undesired side effects of the retinoid. For this type of application the antagonist and/or inverse agonist compound may be administered in a site-specific manner, for example as a topically applied cream or lotion while the co-administered retinoid may be given enterally. For therapeutic applications the antagonist compounds of the invention, like the retinoid agonists compounds, are incorporated into pharmaceutical compositions, such as tablets, pills, capsules, solutions, suspensions, creams, ointments, gels, salves, lotions and the like, using such pharmaceutically acceptable excipients and vehicles which per se are well known in the art. For topical application, the antagonist and/or inverse agonist compounds of the invention could also be administered as a powder or spray, particularly in aerosol form. If the drug is to be administered systemically, it may be confected as a powder, pill, tablet or the like or as a syrup or elixir suitable for oral administration. For intravenous or intraperitoneal administration, the compound will be prepared as a solution or suspension capable of being administered by injection. In certain cases, it may be useful to formulate these compounds by injection. In certain cases, it may be useful to formulate these compounds in suppository form or as extended release formulation for deposit under the skin or intramuscular injection.
The antagonist and/or inverse agonist compounds also, like the retinoid agonists of the invention, will be administered in a therapeutically effective dose. A therapeutic concentration will be that concentration which effects reduction of the particular condition, or retards its expansion. When co-administering the compounds of the invention to block retinoid-induced toxicity or side effects, the antagonist and/or inverse agonist compounds of the invention are used in a prophylactic manner to prevent onset of a particular condition, such as skin irritation.
A useful therapeutic or prophylactic concentration will vary from condition to condition and in certain instances may vary with the severity of the condition being treated and the patient""s susceptibility to treatment. Accordingly, no single concentration will be uniformly useful, but will require modification depending on the particularities of the chronic or acute retinoid toxicity or related condition being treated. Such concentrations can be arrived at through routine experimentation. However, it is anticipated that a formulation containing between 0.01 and 1.0 milligrams of the active compound per mililiter of formulation will constitute a therapeutically effective concentration for total application. If administered systemically, an amount between 0.01 and 5 mg per kg per day of body weight would be expected to effect a therapeutic result.
The term alkyl refers to and covers any and all groups which are known as normal alkyl, branched-chain alkyl, cycloalkyl and also cycloalkyl-alkyl. The term alkenyl refers to and covers normal alkenyl, branch chain alkenyl and cycloalkenyl groups having one or more sites of unsaturation. Similarly, the term alkynyl refers to and covers normal alkynyl, and branch chain alkynyl groups having one or more triple bonds.
Unless specified otherwise, lower alkyl means the above-defined broad definition of alkyl groups having 1 to 6 carbons in case of normal lower alkyl, and as applicable 3 to 6 carbons for lower branch chained and cycloalkyl groups. Lower alkenyl is defined similarly having 2 to 6 carbons for normal lower alkenyl groups, and 3 to 6 carbons for branch chained and cyclo-lower alkenyl groups. Lower alkynyl is also defined similarly, having 2 to 6 carbons for normal lower alkynyl groups, and 4 to 6 carbons for branch chained lower alkynyl groups.
The term xe2x80x9cesterxe2x80x9d as used here refers to and covers any compound falling within the definition of that term as classically used in organic chemistry. It includes organic and inorganic esters. Where B of Formula 1 is xe2x80x94COOH, this term covers the products derived from treatment of this function with alcohols or thiols preferably with aliphatic alcohols having 1-6 carbons. Where the ester is derived from compounds where B is xe2x80x94CH2OH, this term covers compounds derived from organic acids capable of forming esters including phosphorous based and sulfur based acids, or compounds of the formula xe2x80x94CH2OCOR11 where R11 is any substituted or unsubstituted aliphatic, aromatic, heteroaromatic or aliphatic aromatic group, preferably with 1-6 carbons in the aliphatic portions.
Unless stated otherwise in this application, preferred esters are derived from the saturated aliphatic alcohols or acids of ten or fewer carbon atoms or the cyclic or saturated aliphatic cyclic alcohols and acids of 5 to 10 carbon atoms. Particularly preferred aliphatic esters are those derived from lower alkyl acids and alcohols. Also preferred are the phenyl or lower alkyl phenyl esters.
The term amides has the meaning classically accorded that term in organic chemistry. In this instance it includes the unsubstituted amides and all aliphatic and aromatic mono- and di-substituted amides. Unless stated otherwise in this application, preferred amides are the mono- and di-substituted amides derived from the saturated aliphatic radicals of ten or fewer carbon atoms or the cyclic or saturated aliphatic-cyclic radicals of 5 to 10 carbon atoms. Particularly preferred amides are those derived from substituted and unsubstituted lower alkyl amines. Also preferred are mono- and disubstituted amides derived from the substituted and unsubstituted phenyl or lower alkylphenyl amines. Unsubstituted amides are also preferred.
Acetals and ketals include the radicals of the formula-CK where K is (xe2x80x94OR)2. Here, R is lower alkyl. Also, K may be xe2x80x94OR7Oxe2x80x94 where R7 is lower alkyl of 2-5 carbon atoms, straight chain or branched.
A pharmaceutically acceptable salt may be prepared for any compound in this invention having a functionality capable of forming a salt, for example an acid functionality. A pharmaceutically acceptable salt is any salt which retains the activity of the parent compound and does not impart any deleterious or untoward effect on the subject to which it is administered and in the context in which it is administered.
Pharmaceutically acceptable salts may be derived from organic or inorganic bases. The salt may be a mono or polyvalent ion. Of particular interest are the inorganic ions, sodium, potassium, calcium, and magnesium. Organic salts may be made with amines, particularly ammonium salts such as mono-, di- and trialkyl amines or ethanol amines. Salts may also be formed with caffeine, tromethamine and similar molecules. Where there is a nitrogen sufficiently basic as to be capable of forming acid addition salts, such may be formed with any inorganic or organic acids or alkylating agent such as methyl iodide. Preferred salts are those formed with inorganic acids such as hydrochloric acid, sulfuric acid or phosphoric acid. Any of a number of simple organic acids such as mono-, di- or tri-acid may also be used.
Some compounds of the present invention may have trans and cis (E and Z) isomers. Unless specific orientation of substituents relative to a double bond or a ring is indicated in the name of the respective compound, and/or by specifically showing in the structural formula the orientation of the substituents relative to the double bond or ring the invention covers trans as well as cis isomers.
Some of the compounds of the present invention may contain one or more chiral centers and therefore may exist in enantiomeric and diastereomeric forms. The scope of the present invention is intended to cover all isomers per se, as well as mixtures of cis and trans isomers, mixtures of diastereomers and racemic mixtures of enantiomers (optical isomers) as well.
The compounds of the invention, can generally speaking be obtained by a series of reactions as disclosed in Reaction Scheme 1. Referring now to Reaction Scheme 1, the starting compound in this synthetic route is a dihydronaphthalene, chromen, thiochromen or dihdroquinoline of Formula 2 where the symbols X, R3 and R4 are defined as in connection with Formula 1, and where X1 represents a leaving group, such as chloro, bromo or trifluoromethylsulfonyloxy (CF3SO3, triflate) group. Generally speaking the starting dihydronaphthalene compound is available in accordance with the chemical scientific or patent literature, or can be prepared by such modifications of published procedures which are readily within the skill of the practicing organic chemist. The ensuing detailed description provides the literature sources of or synthetic procedures for preparing certain examples of the starting compounds of Formula 2. Examples of chroman-4-one and thiochroman-4-one derivatives which can be readily converted into the chromen and thiochromen derivatives within the scope of Formula 2 or Formula 5 can be found in the patent or other chemical literature, for example in the publication Johnson et al. Biorganic and Medicianal Chemistry 7 (1999) 1321-1338 (e.g. 6-methoxy-2,2-dimethyl-thiochroman-4-one; 2,2-dimethyl-4-oxo-thiochroman-6-yl trifluoromethanesulfonate; 2,2-dimethyl-6-bromo-thiochroman-4-one; 6-methoxy-2,2-dimethyl-chroman-4-one; 2,2-dimethyl-4-oxo-chroman-6-yl trifluoromethanesulfonate; 2,2-dimethyl-6-bromo-chroman-4-one; 6-methoxy-thiochroman-4-one; 4-oxo-thiochroman-6-yl trifluoromethanesulfonate; 6-bromo-thiochroman-4-one; 6-methoxy-chroman-4-one; 4-oxo-chroman-6-yl trifluoromethanesulfonate; 6-bromo-chroman-4-one).
Referring now to Reaction Scheme 1, the dihydronaphthalene, chromen or thiochromen derivative of Formula 2 is reacted with an aromatic or heteroaromatic amine of Formula 3, where the symbols Y, R2, A and B are defined as in connection with Formula 1. Examples for the aryl or heteroaryl amines of Formula 3 are ethyl 4-aminobenzoate, ethyl 3-aminobenzoate, ethyl 6-aminopyridine-3-carboxylate, ethyl 6-aminopyridine-2-carboxylate, ethyl 5-aminothiophen-3-carboxylate, ethyl 5-aminothiophen-2-carboxylate, ethyl 5-aminofuran-3-carboxylate and ethyl 5-aminofuran-2-carboxylate. Generally speaking the aryl or heteroaryl amines of Formula 3 are available from the chemical literature, or can be made by such modifications of known processes which are readily apparent to the practicing synthetic organic chemist. The compound of Formula 2 is reacted with the aryl or heteroaryl amine of Formula 3 by heating, preferably in an aprotic solvent such as toluene and preferably in the presence of a catalysts, such as palladium(2) acetate (Pd(OAc)2) and (S)-(xe2x88x92)-2,2xe2x80x2-bis(diphenylphosphino)1,1xe2x80x2-binaphthyl (BINAP) and an acid acceptor such as cesium carbonate (CsCO3). The result of this type of reaction is a dihydronaphthalenyl, chromenyl or thichromenyl and aryl or heteroaryl substituted amine of Formula 4. 
Still, as it is shown in Reaction Scheme 1, the secondary amine of Formula 4 can also be obtained by reacting a dihydronaphthalenyl, chromenyl or thiochromenyl amine of Formula 5 with a reagent of Formula 6 where X2 represents a halogen, preferably iodine or bromine, and the remaining symbols are defined as in connection with Formula 1. The reagents of Formula 6 are halogen substituted aryl or heteroaryl compounds which, generally speaking, can be obtained by reactions well known in the art. An example of such a compound is ethyl 4-iodobenzoate which is obtainable, for example, by esterification of 4-iodobenzoic acid. This esterification reaction is described in U.S. Pat. No. 5,616,712 incorporated herein by reference. Other examples for the reagents of Formula 6 are ethyl 4-bromobenzoate, ethyl 6-iodonicotinate (obtainable by halogen exchange reaction on 6-chloronicotinic acid followed by esterification), ethyl 6-fluoronicotinate, ethyl 6-chloronicotinate, ethyl 5-iodo or 5-bromothiophene-2-carboxylate and ethyl 5-iodo or 5-bromofuran-2-carboxylate. The reaction of the amine of Formula 5 with the halogen substituted aryl or heteroaryl compound of Formula 6 is preferably conducted in the presence of the catalysts tris(dibenzylideneacetone)dipalladium(0)(Pd2(dba)3) , and (S)-(xe2x88x92)-2,2xe2x80x2-bis(diphenylphosphino)1,1xe2x80x2-binaphthyl (BINAP) in the presence of an acid acceptor, such as cesium carbonate, while being heated in an inert solvent (toluene) in an inert gas atmosphere.
The resulting aryl or heteroaryl, dihydronaphthalenyl amines (disubstituted amines) of Formula 4 are within the scope of the invention, but can be converted to the preferred trisubstituted amines of Formula 1, also within the scope of the invention, by reaction with a reagent of the formula R1-X3 where R1 is defined as in connection with Formula 1, and X3 is halogen, preferably iodine or bromine. The reaction of the disubstituted amines of Formula 4 with the reagent R1-X3 will be recognized by those skilled in the art as an xe2x80x9calkylationxe2x80x9d or analogous reaction, and is preferably conducted by heating in an aprotic polar solvent, such as dimethylacetamide, in the presence of an acid acceptor, such as potassium carbonate. Alternatively, the secondary amines of Formula 4 are converted into the preferred tertiary amines of Formula 1 by a reductive alkylation reaction that employs the aldehyde reagent R1*xe2x80x94CHO, sodium cyanoborohydride and acetic acid usually in acetonitrile or tetrahydrofuran (THF) as the solvent. The group R1*xe2x80x94 is defined to the extent it can be made applicable, as the group R1 in Formula 1 with one less CH2 unit, that is a homolog having one CH2 unit (carbon atom) less than the group R1.
The primary amine compounds of Formula 5 can be obtained from the compounds of Formula 2 by reactions known in the art, for example by reaction of the compounds of Formula 2 with benzophenone imine, as is shown in the reaction scheme.
Still another alternative route for the synthesis of the tertiary amines of Formula 1 is through alkylation of the compounds of Formula 5 with the reagent R1-X3 (or reductive alkylation with the reagent R*xe2x80x94CHO) to yield the dihydronapthalenyl, chromenyl or thiochromenyl alkyl amines of Formula 5a, which are thereafter reacted with the reagent of Formula 6.
The trisubstituted amine compounds of Formula 1 can be converted into further homologs and derivatives, still within the scope of the invention, by such reactions as esterification, saponification, homologation, reduction to aldehyde or alcohol stage and the like, which per se are well known in the art. These reactions usually involve transformations of the groups designated A and B in the formulas but are not necessarily limited to those. Some of the known and published general principles and synthetic methodology employed in the transformations of the A and B groups are briefly described below.
Carboxylic acids are typically esterified by refluxing the acid in a solution of the appropriate alcohol in the presence of an acid catalyst such as hydrogen chloride or thionyl chloride. Alternatively, the carboxylic acid can be condensed with the appropriate alcohol in the presence of dicyclohexylcarbodiimide (DCC) and 4-(dimethylamino)pyridine (DMAP). The ester is recovered and purified by conventional means. Acetals and ketals are readily made by the method described in March, xe2x80x9cAdvanced Organic Chemistry,xe2x80x9d 2nd Edition, McGraw-Hill Book Company, p 810). Alcohols, aldehydes and ketones all may be protected by forming respectively, ethers and esters, acetals or ketals by known methods such as those described in McOmie, Plenum Publishing Press, 1973 and Protecting Groups, Ed. Greene, John Wiley and Sons, 1981.
The acids and salts derived from compounds of the invention are readily obtainable from the corresponding esters. Basic saponification with an alkali metal base will provide the acid. For example, an ester of the invention may be dissolved in a polar solvent such as an alkanol, preferably under an inert atmosphere at room temperature, with about a three molar excess of base, for example, lithium hydroxide or potassium hydroxide. The solution is stirred for an extended period of time, between 15 and 20 hours, cooled, acidified and the hydrolysate recovered by conventional means.
The amide may be formed by any appropriate amidation means known in the art from the corresponding esters or carboxylic acids. One way to prepare such compounds is to convert an acid to an acid chloride and then treat that compound with ammonium hydroxide or an appropriate amine. For example, the ester is treated with an alcoholic base solution such as ethanolic KOH (in approximately a 10% molar excess) at room temperature for about 30 minutes. The solvent is removed and the residue taken up in an organic solvent such as diethyl ether, treated with a dialkyl formamide and then a 10-fold excess of oxalyl chloride. This is all effected at a moderately reduced temperature between about xe2x88x9210 degrees and +10 degrees C. The last mentioned solution is then stirred at the reduced temperature for 1-4 hours, preferably 2 hours. Solvent removal provides a residue which is taken up in an inert organic solvent such as benzene, cooled to about 0 degrees C. and treated with concentrated ammonium hydroxide. The resulting mixture is stirred at a reduced temperature for 1-4 hours. The product is recovered by conventional means.
Alcohols are made by converting the corresponding acids to the acid chloride with thionyl chloride or other means (J. March, xe2x80x9cAdvanced Organic Chemistryxe2x80x9d, 2nd Edition, McGraw-Hill Book Company), then reducing the acid chloride with sodium borohydride (March, Ibid, pg. 1124), which gives the corresponding alcohols. Alternatively, esters may be reduced with lithium aluminum hydride at reduced temperatures. Alkylating these alcohols with appropriate alkyl halides under Williamson reaction conditions (March, Ibid, pg. 357) gives the corresponding ethers. These alcohols can be converted to esters by reacting them with appropriate acids in the presence of acid catalysts or dicyclohexylcarbodiimide and dimethylaminopyridine.
Aldehydes can be prepared from the corresponding primary alcohols using mild oxidizing agents such as pyridinium dichromate in methylene chloride (Corey, E. J., Schmidt, G., Tet. Lett., 399, 1979), or dimethyl sulfoxide/oxalyl chloride in methylene chloride (Omura, K., Swern, D., Tetrahedron, 1978, 34, 1651).
Ketones can be prepared from an appropriate aldehyde by treating the aldehyde with an alkyl Grignard reagent or similar reagent followed by oxidation.
Acetals or ketals can be prepared from the corresponding aldehyde or ketone by the method described in March, Ibid, p 810.
The preferred compounds of the invention are dihydronaphthalene derivatives (X=C(R)2) and R is preferably methyl. With reference to the symbol Y in Formula 1 the preferred compounds of the invention are those where Y is phenyl, naphthyl, pyridyl, thienyl or furyl. Even more preferred are compounds where Y is phenyl or pyridyl. As far as substitutions on the Y (phenyl) and Y (pyridyl) groups are concerned, compounds are preferred where the phenyl group is 1,4 (para) substituted and where the pyridine ring is 2,5 substituted. (Substitution in the 2,5 positions in the xe2x80x9cpyridinexe2x80x9d nomenclature corresponds to substitution in the 6-position in the xe2x80x9cnicotinic acidxe2x80x9d nomenclature.) In the presently preferred compounds of the invention there is no R2 substituent (other than hydrogen) on the Y group. When there is an R2 substituent it is preferably lower alkyl or halogen.
The A-B group of the preferred compounds is (CH2)qCOOH or (CH2)qxe2x80x94COOR8, where R8 is defined as above. Even more preferably q is zero and R8 is lower alkyl or the compound is a carboxylic acid, or a pharmaceutically acceptable salt thereof.
R1 is preferably an alkyl or allyl group, Among the alkyl groups methyl, ethyl, branched-chain alkyl and cyclopropylmethyl groups are preferred. In this regard it should be noted that in the definition of this invention the term alkyl includes cycloalkyl and cycloalkylalkyl groups as well.
The integer m is preferably 0 (zero) meaning that there is no R3 substituent, or m=1 and in such case the R3 substituent is preferably lower alkyl, or alkoxy even more preferably methyl, methoxy or ethoxy. The R3 substituent is preferably in the 2 or 3 position of the dihydronaphthalene nucleus, as these positions are indicated in Formula 7 below. The substituted amino groups are preferably in the otherwise unoccupied 2 or 3 position of the dihydronaphthalene nucleus, as these positions are indicated in Formula 7 below. Those skilled in the art will recognize that when the compounds of the invention and the intermediates leading thereto are given appropriate chemical names these positions may have a different number. However, the precise structures of the compounds of the invention are disclosed clearly with reference to the structural formulas provided below. 
Referring now to the integer o in Formula 1, preferably o=1. In other words, the non-aromatic ring of the dihydronaphthalene moiety is preferably substituted with an R4 group in the 8 position. It is also preferably substituted with geminal dimethyl groups in the 5 position (as indicated in Formula 7). A lower alkyl group for the 8 position, (R4) is particularly preferred.
The most preferred compounds of the invention are disclosed in Table 2 with reference to Formulas 8 and 9. 

Reaction Scheme 2 discloses the presently preferred synthesis of certain exemplary compounds of the invention where the dihydronaphthalene moiety is substituted in its 2-position (as defined in Formula 7) with an arylamine. In accordance with this reaction scheme, a secondary amine of the type shown in Formula 4 in Scheme 1 is obtained by reaction of a 2-trifluoromethylsulfonyloxy-dihydronaphthalene derivative with ethyl 4-aminobenzoate. The secondary amine is converted into the preferred tertiary amines of the invention by reductive alkylation, employing acetaldehyde in the presence of sodium cyanoborohydride and acetic acid in acetonitrile or tetrahydrofuran (THF).
Reaction Scheme 3 discloses another example of a synthetic route leading to certain preferred compounds of the invention where the dihydronaphthalene moiety is substituted in its 2- and 8-positions with a methyl group and in the 3-position with an arylamine. In this exemplary synthetic route also, the secondary amines of the type of Formula 4 in Scheme 1 are obtained by reaction of the corresponding trifluoromethylsulfonyloxy-dihydronaphthalene derivatives, (3-trifluoromethylsulfonyloxy-dihydronaphthalene derivatives) with ethyl 4-aminobenzoate. The secondary amine is converted into the exemplary preferred tertiary amines of the invention by reductive alkylation, employing formaldehyde, acetaldehyde, propionaldehyde and cyclopropylformaldehyde, respectively. Reaction Scheme 4 discloses the synthesis of examples analogous to those shown in Scheme 3, however in Scheme 4 the dihydronaphthalene moiety is substituted with a methyl group in its 2-position and respectively with iso-propyl, ethyl and tertiary-butyl groups on its 8-position. In this scheme also, the secondary amines are obtained by displacement of 3-trifluoromethylsulfonyloxy-dihydronaphthalene derivatives with ethyl 4-aminobenzoate and the secondary amines are converted into the exemplary preferred tertiary amines of the invention by reductive alkylation. 
Reaction Scheme 5 discloses presently preferred synthetic routes for making certain preferred compounds of the invention where the dihydronaphthalene moiety is substituted in its 3-position with an arylamine and where the 2-position is unsubstituted. In these examples of synthesis the starting compound is 6-bromo-4,4-dimethyl-1,2,3,4-tetrahydronaphthalene-1-one which is available in accordance with U.S. Pat. No. 5,489,584, the specification of which is expressly incorporated herein by reference. After an alkyl substituent is introduced into the dihydronaphthalene nucleus by subjecting the carbonyl carbon to a Grignard (or like) reaction, the bromo atom is replaced with an NH2 group by reaction with benzophenoneimine in the presence of the catalysts tris(dibenzylideneacetone)dipalladium(0) (Pd2(dba)3), (S)-(xe2x88x92)-2,2xe2x80x2-bis(diphenylphosphino)1,1xe2x80x2-binaphthyl (BINAP) and sodium tertiary-butoxide. The preferred tertiary amines of the invention are also obtained in this scheme by reductive alkylation. 
Reaction Scheme 6 provides an exemplary synthetic route for preparing preferred compounds of the invention where the dihydronaphthalene moiety is substituted with a tertiary-butyl group in its 8-position and with an arylamine in its 2-position. In this synthetic process the starting compound is 7-bromo-1-(1,1-dimethylethyl)-3,4-dihydro-4,4-dimethylnaphthalene which is available in accordance with the U.S. Pat. No. 5,763,635, the specification of which is incorporated herein by reference. This starting compound is converted into the corresponding amino derivative by reaction with benzophenoneimine, as is described above in connection with Reaction Scheme 5. The amino substituted dihydronaphthalene is thereafter reacted with ethyl 4-iodobenzoate in the presence of the catalysts tris(dibenzylideneacetone)dipalladium(0) (Pd2(dba)3), (S)-(xe2x88x92)-2,2xe2x80x2-bis(diphenylphosphino)1,1xe2x80x2-binaphthyl (BINAP) and cesium carbonate. The resulting secondary amines are converted into the preferred tertiary amines of the invention by alkylation with ethyl iodide, n-propyliodide and allyl bromide, respectively.
Reaction Scheme 7 provides an exemplary synthetic route for preparing preferred compounds of the invention where the dihydronaphthalene moiety is substituted with methyl, ethyl, iso-propyl and tertiary-butyl groups, respectively, in its 8-position, with an arylamine in its 2-position and with an O-alkyl group in its 3 position. The starting compound for this synthetic route is methoxyphenol (anisol). The coupling reaction of a 2-bromo-dihydronaphthalene derivative with ethyl 4-aminobenzoate is conducted in the presence of the catalysts tris(dibenzylideneacetone)dipalladium(0) (Pd2(dba)3) and 2-dicyclohexylphosphino-2xe2x80x2-(N,N-dimethylamino)biphenyl (Cy-MAP) which is commercially available from Strem Chemicals Inc. Newburtyport Mass. (see also J. Am. Chem. Soc., 1998, 120, 9722 and J. Am. Chem. Soc., 1999, 121, 6090.)
Reaction Scheme 8 provides an exemplary synthetic route for preparing preferred compounds of the invention where the dihydronaphthalene moiety is substituted with methyl, ethyl, iso-propyl and tertiary-butyl groups, respectively, in its 8-position, and with a 6-amino-pyridine-3-carboxylic acid residue in the 2 position. The starting compounds for these syntheses are the 2-bromo-8-methyl-, 2-bromo-8-ethyl-, 2-bromo-8-i-propyl-, and 2-bromo-8-t-butyl-5,6-dihydronaphtalenes which are available in accordance with the state of the art. The tertiary-butyl compound is described for example in U.S. Pat. No. 5,763,635, incorporated herein by reference. The 2-bromo-8-methyl-, 2-bromo-8-ethyl-, 2-bromo-8-i-propyl-, and 2-bromo-8-t-butyl-5,6-dihydronaphtalenes, respectively, are converted to the 2-amino derivatives by reaction with benzophenone-imine, and this is followed by acetylation of the primary amino group to provide the corresponding acetamides. The acetamides are reduced with LiAlH4 to give the corresponding 2-dihydronaphtalenyl-ethyl amides, and these are reacted with 6-fluoro-pyridine-3-carboxylic acid by heating in an aprotic solvent, such as toluene, to provide exemplary preferred compounds of the invention which are nicotinic acid derivatives.
Detailed description of the steps of the processes illustrated in Reaction Schemes 2-8 are provided below in the experimental section. 